A typical laser device of relatively few parts is disclosed and described in the copending application of Karl G. Hernqvist, Ser. No. 462,506, filed Apr. 19, 1974, U.S. Pat. No. 3,904,986 issued on Sept. 9, 1975. A laser device of this type comprises a tubular envelope, typically of a glass tube, having its two ends closed by metal end plates. Within the tube is mounted a laser bore member consisting substantially of a glass tube of small diameter extending coaxially within the glass tube of the envelope. Also, a metal cathode cylinder electrode extends within the laser envelope adjacent to one end and is electrically connected to the metal end plate closing that one end, which in turn provides an external electrical lead to the cathode cylinder. The other end plate closing the opposite end of the envelope tube provides the anode electrode of the laser device. Both of the end plates have central apertures aligned with the axis of the bore tube. On the outer surface respectively of each end plate is mounted a mirror block having a surface bonded to and closing the aperture of the end plate. Aligned with each end plate aperture and normally formed on the surface of the block closing the aperture is an optical mirror. The two mirrors, one formed on each block, together with the bore tube provide the optical lasing cavity of the laser device.
It is common practice to bond the mirror blocks to end plates of the laser with an epoxy adhesive material. An epoxy adhesive is used, since this allows the joining of the mirror blocks to the end plates at a relatively low temperature. The use of high temperatures to provide a bond between the mirror block and the respective end plate endangers the mirror coatings used in forming the mirrors. However, the disadvantage of using an epoxy adhesive is the relatively short life that an epoxy system provides. Over a period of time, in the order of one year or so, the epoxy adhesive deteriorates and loses its adhesive value. This enables the mirror blocks to become loose and become separated from the end plates thus ending the life of the laser device. Greater operating life is necessary for lasers used in video playback, facsimile and information retrieval applications, for example.